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Question about RLa-a for *LW6 in triode connection?
Question about RLa-a for *LW6 in triode connection?
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Old 16th June 2018, 03:18 PM   #21
jazbo8 is offline jazbo8
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Question about RLa-a for *LW6 in triode connection?
Can't be 200mA then... just to make sure, you are still planning to build a 36LW6 triode-connected PP amp, right?
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Old 16th June 2018, 04:57 PM   #22
Tubelab_com is offline Tubelab_com  United States
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If I was to try the LW6 in P-P triode I would try 275 to 300 volts. That's the G2 spec plus a little bit.

I'm trying to burn through the wife's honey-do list of outdoor tasks while it isn't raining. That has allowed me only one indoor day this week and I spent that replacing the motherboard in my other PC that unexpectedly checked out in the middle of a video editing session last week. Unfortunately her list is growing faster than I can cross stuff off the list......but it's got to rain sometime.

Tomorrow it's off to her father's house for Fathers day. I get to let the grandkids throw water balloons at me until they run out of ammo.

I have a driver board that can drive the grids out af near any tube made, a box full of LW6's and a selection of suitable OPT's. Should be easy to try something like 300 volts in triode into 1250 ohms.

Quote:
they appear to be more suitable for Class aB operation in order to keep the idling power as low as possible.
Horizontal (line output) sweep tubes were never designed for class A operation. It has been stated that the most linear part of the curves lie in the red zone. Vertical (frame output) sweep tubes are DESIGNED for class A operation, but the biggest ones are only good for 15 watts or so. I'm sure that an LW6 can work in class A triode, but how much power will it make, and under what conditions remain unknown. Perhaps a point where the first 10 watts of so can come in class A with more power available in AB.

There are several different varieties of LW6's. The internals are probably all similar but there are several variations of heat radiating fins attached to the plates, as well as none at all. There are also two different bottle diameters.

All the Sylvania made tubes have no supplemental fins and the smallest bottle, even still it takes 60+ watts to get a faint redness in a dark room. It was a well used Sylvania that I torture tested to 600+ watts, not a GE like I thought. The tube is still in the test socket.

There are several different GE fin structures and two bottle diameters. The fattest tubes with the large wrap around fins need 80 to 90 watts to provoke glow.....but those are the ones I had trouble with. I was initially running them at around 40 watts, and went down as I lowered the B+.
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Old 16th June 2018, 05:54 PM   #23
jazbo8 is offline jazbo8
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Question about RLa-a for *LW6 in triode connection?
Quote:
Originally Posted by smoking-amp View Post
a) 36LW6 in triode, 50 V/div horiz., 50 mA/div vert., Mu approx. 3.7 at 125 mA
Something don’t quite add up - from the M-2057 datasheet, Ep=Eg2=250V, Eg1=-85V, Ip=125mA, couldn’t get anywhere near it according to the traced curves.
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Old 16th June 2018, 07:04 PM   #24
Tubelab_com is offline Tubelab_com  United States
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The M2057 data sheet shows -56 volts G1 for 125 mA at 250 volts. -85 is the value for 1 mA (near cutoff).
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Old 16th June 2018, 07:30 PM   #25
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Question about RLa-a for *LW6 in triode connection?
Right, I got to squint harder...
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Old 22nd June 2018, 02:53 AM   #26
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Ok. so I ran some sims with Push-Pull Calculator and I'm thinking triode connected with a B+ of 220V and Ia of about 100ma and RLa-a of 1k25. It should make 35W, 15W class a limit.
Apparently this doesn't exceed any specs.

Thoughts?

Here's what I'm thinking, minus the power supply, of course.
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File Type: png 6F12P-36LW6-fixed-bias.png (54.5 KB, 81 views)
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Old 22nd June 2018, 04:48 AM   #27
multi is offline multi  Australia
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35 Watts, 15 watts class A is close to what you get from a KT88/6550 at 400/450 volts at only 220volts?

maybe I will try such an amp

would it be possible to use a EL509 as triode. what voltage?

Thanks
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File Type: pdf el509bpt_as_triode.pdf (15.7 KB, 13 views)
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Old 22nd June 2018, 06:42 AM   #28
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Question about RLa-a for *LW6 in triode connection?
Quote:
Originally Posted by kodabmx View Post
Ok. so I ran some sims with Push-Pull Calculator and I'm thinking triode connected with a B+ of 220V and Ia of about 100ma and RLa-a of 1k25.
Which parameters did you use for the tube? I'm not getting the same results.
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Old 22nd June 2018, 02:49 PM   #29
kodabmx is offline kodabmx  Canada
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I effectively treated it as if it was 2 2A3s in parallel and went from there. I'm also not sure if PPcalc is working properly as I have to tweak different settings to get coherent results.


What settings are you using?

Last edited by kodabmx; 22nd June 2018 at 02:52 PM.
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Old 22nd June 2018, 02:52 PM   #30
jazbo8 is offline jazbo8
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Question about RLa-a for *LW6 in triode connection?
I see, I ran the simulation based on smoking-amp’s curves, that’s why the results were different.
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